DE 198 44 465 A1 describes a current-measuring circuit arrangement which uses a current mirror circuit, and which has a first branch and a second branch, wherein the consumer is connected to the first branch and an evaluation circuit to the second branch. The first branch consists of a series circuit of a shunt resistor, a transistor, two additional resistors and a switching transistor with grounded emitter. An ohmic load as the consumer is connected at the node connecting the shunt resistor and the first-mentioned transistor. The second branch of the current mirror circuit consists of a series circuit of a resistor, a transistor, and another resistor, wherein the current mirror circuit is realized by connecting the base terminals of the two transistors. Furthermore, it is specified there that a Zener diode is connected in parallel with the circuit consisting of shunt resistor, first transistor, and resistor in the first branch of the current mirror circuit in order to regulate the voltage. In this circuit arrangement, the current flowing through the shunt resistor branches at the current mirror circuit, so that a first partial current flows through the consumer and a second partial current flows through the first branch of the current mirror circuit. Thus, the current in the second branch of the current mirror circuit is not identical to the current being measured through the consumer, so that the measurement accuracy for measuring the current through the consumer is poor, and this document also indicates that it is only around 5%. Moreover, the consumer is of relatively low resistance, since it is intended to be a motor vehicle headlight. Therefore, the load current is on the order of about 4 A to 12 A.
U.S. Pat. No. 5,845,275 shows a circuit arrangement for measuring an electric current with a nonlinear element for the current-to-voltage conversion in the form of a fuzzy logic processor with a nonlinear semiconductor element.
EP 1 298 778 A2 describes a constant-current source, in the control loop of which a sawtooth generator is used.
EP 1 372 261 A1 shows a current measurement circuit with a current mirror circuit made up of MOS transistors. The circuit there is used to control the current for a photodiode.
Finally, EP 1 211 776 A2 describes an inductive power distribution system with a circuit that is intended to hold the output voltage within given limits when resonances appear due to inductances.